Long-Term Debt - Summary of Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total principal amount	$ 169,649	$ 173,695
Finance lease liabilities	52	60
Less: unamortized discount and issuance costs	(7,810)	(10,000)
Total long-term debt	161,839	163,695
4.25% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Total principal amount	139,200	143,750
3.95% Promissory Note [Member]
Debt Instrument [Line Items]
Total principal amount		8,881
4% Promissory Note [Member]
Debt Instrument [Line Items]
Total principal amount	7,081	7,345
3.75% Callable Promissory Note [Member]
Debt Instrument [Line Items]
Total principal amount	7,783	7,955
4.55% Promissory note [Member]
Debt Instrument [Line Items]
Total principal amount	5,588	$ 5,704
3.90% Promissory Note [Member]
Debt Instrument [Line Items]
Total principal amount	$ 9,945